A 12-year-old child presents with a rigid flat foot that does not correct on tiptoeing. CT scan reveals a bony coalition between the calcaneus and navicular bones. The most common type of tarsal coalition associated with peroneal spastic flatfoot is:
- A Talocalcaneal coalition (middle facet)
- B Talocalcaneal coalition (anterior facet)
- C Calcaneonavicular coalition ✓
- D Calcaneocuboid coalition
Correct answer: C. Calcaneonavicular coalition
Explanation
Calcaneonavicular coalition is the most common tarsal coalition, accounting for approximately 50% of cases. Talocalcaneal coalition (middle facet) is the second most common. Both can cause peroneal spastic flatfoot due to restricted subtalar motion causing reactive peroneal muscle spasm. Calcaneonavicular coalition is typically visible on a 45° oblique foot radiograph as an elongated anterior calcaneal process (anteater sign).
Reference: Herring's Tachdjian's Pediatric Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.